Field of the Invention and Related Art Statement
This invention relates to a parent-and-son type endoscope system for making an observation with a first endoscope and a second endoscope used as combined as by being inserted into a channel of the first endoscope.
Recently, endoscopes have come to be extensively used not only in the medical field but also in the industrial field.
Such a endoscope is provided with a channel insertable through a treating instrument so that a therapeutic treatment may be made with the treating instrument.
There is a case that an endoscope having an insertable section of a fine diameter is inserted through this channel and is used as a parent-and-son type endoscope. A parent-and-son type endoscope system using parent and son endoscopes is disclosed in the publication of Japanese Patent Application Laid Open No. 234834/1986.
In this prior art example, it is disclosed that an image of a TV camera externally fitted scope with a TV camera fitted to a parent side video scope or fiber scope and an image of a son side video scope or TV camera externally fitted scope are displayed in one TV monitor by an image mixer.
In this prior art example, in case a simultaneous type video scope or TV camera whereby an imaging is made by an imaging means provided with a color separating filter under an illumination of a white light is used, no problem will be produced but, in case a field sequential type video scope or TV camera whereby a sequential imaging is made under respective illuminating lights of different wavelength ranges is used, unless the R,G,B lights (field sequential lights) on the parent side and son side are synchronized, there will be problems that the colors will not be able to be reproduced, Further a light in another illuminating period will enter a solid state imaging device forming the imaging means in one blanking period, therefore a smear or blooming will be generated and the picture quality will deteriorate.
That is to say, in the field sequential type imaging system, an object to be imaged is illuminated with a field sequential light by a field sequential type illuminating means and the light reflected from the object is made to form an image on the imaging surface of such solid state imaging device as a CCD having no color separating filter through an objective optical system. A signal accumulated as a charge or the like photoelectrically converted by applying a driving signal to the solid state imaging device is read out in the next light intercepting period and is once memorized as a component image in the respective memories corresponding to the respective field sequential lights. When a plurality of component images corresponding to one color image are memorized, they will be simultaneously read out to produce a color video signal.
Therefore, unless the illuminating states of two field sequential type video scopes are substantially synchronized with each other, the colors will not be able to be reproduced. For example, when the field sequential light of one video scope apparatus is red but the field sequential light of the other video scope apparatus is green, the component image obtained by these added lights will be processed as red and green component images in the respective apparatus. In this case, there is a problem that the signal level of the red component image will become large in one video scope apparatus. That is, the color reproductivity will be obstructed. This problem will be produced even if not only a line transfer type but also interline transfer type and frame transfer type of solid state imaging devices are used.
Also, when one video scope apparatus is in an illuminating state (period) but the other video scope apparatus is in a signal reading state (period), in this reading state, a charge transfer will be made on the imaging surface. Therefore in the case of a solid state imaging device in which the imaging section and transfer section are of a common line transfer type and are adapted to be made small, a photoelectrically converted signal caused by the illuminating light of one apparatus will be mixed with a signal being transferred and will produce a smear. Also, due to the mixed signal, the signal level will rise and will overflow the periphery to cause a blooming.
These defects will be generated not only in the parent-and-son type endoscope system but also in the case of using two endoscopes as combined.